Compaction loading apparatus

ABSTRACT

A stationary loading and compacting mechanism particularly for injecting waste material into and pressurizing it within a large reinforced container comprises a ramming chamber to which the container to be loaded is detachably coupled, the chamber having a top charging opening into which waste material is dumped and a front outlet or ramming port alignable with a receiving port in the container. A multisectioned rectangular ram assembly consisting of lower and upper ram sections is movable through the ramming chamber and ports and part way into the container to force the material into and compress it within the container, the two sections of the ram being movable both as a unit and to a limited extent independently of each other.

United States Patent 15 Claims, 13 Drawing Figs.

US. Cl 100/50, 100/229 A, 100/269, 100/295 Int. B3011 15/22 Field of Search 100/50, 53, 229, 269, 295, 214, 215; 53/124 References Cited UNITED STATES PATENTS 3,037,446 6/1962 Thompson 100/295 UX Inventor App!v No. Filed Patented Assignee COMPACTION LOADING APPARATUS 3,103,876 9/1963 Ferranti 100/295 X r 3,303,946 2/1967 Wilkins .1 100/229 UX 3,384,007 5/1968 Boje et al 100/229 X Primary Examiner-Billy .lv Wilhite AnomeyPrice. Heneveld, Huizenga & Cooper ABSTRACT: A stationary loading and compacting mechanism particularly for injecting waste material into and pressurizing it within a large reinforced container comprises a ramming chamber to which the container to be loaded is detachably coupled, the chamber having a top charging opening into which waste material is dumped and a front outlet or ramming port alignable with a receiving port in the container. A multisectioned rectangular ram assembly consisting of lower and upper ram sections is movable through the ramming chamber and ports and part way into the container to force the material into and compress it within the container, the two sections of the ram being movable both as a unit and to a limited extent independently of each other.

PATENTED SEP 7 l9?! SHEET 1 UF 9 INVENTOIQ.

iar/ PATENTED SEP mm 3.603 245 SHEET 2 [IF 9 INVENTOR.

PATENTED SEP 7 1971 SHE INVENTOR.

fa /r2 33:94.

PATENTEUSEP 7H7! 3.603245 sum 9 OF 9 p ua INVENTOR.

diam 1 5469?.

COMPACTION LOADING APPARATUS.

BACKGROUND owns INVENTION Stationary compaction apparatus of the type disclosed in priorU.S; Pat. Nos. 3,250,4l4,3,289,572 and 3,403,620 and t which are designed ,tohandle virtually all-types of .waster material from household, industrial, commercial and other activities are finding increasingusage in connection withwaste handling operations of increasing magnitude. Such operations includelarge "transfer stations," wherein truckloads of waste material are dumped into chutes leadingdownwardly into a ramming chamber. The trucks or other sources of waste material may be on an upper. floor and the compactionapparatus out of sight on a lower floor.

Animportant object of the present inventionis to provide improved means whereby material can be charged into chute and/or hopper at the top of the compaction apparatus at any time regardless of the position of the ram andwithoutinterfering with proper operation.ofthecompactor. Another object is to incorporate improved means for preventing unusually large rigid objects or overloads which arehot compressible without overstressing the equipment from interfering with proper operation of the apparatus and for eliminating any obstructing or overloading difficulty which may arise. Another object is to. achieve more efficient and quicker loading and compaction of containers.

Otherobjects and advantages will. be apparent on consideration of the present disclosure in its entirety.

BRIEF DESCRIPTION OF THE FIGURES OF DRAWING FIG. 1 is a side elevational view partly broken away of a stationary compactor incorporating the principles of the present invention; g

FIG. '2 is a longitudinalsectional viewof the rear portionv thereof on a larger scale, also partly broken away;

FIGS. 3,-4 and 5 are cross-sectionalviews taken respectively on the lines lII-III, IV-IV, and V--V respectively of FIG. 2 but on a larger scale and looking in the directionof the arrows;

FIG. 6 is a schematic diagram of the hydraulic control system;

FIGS. 7A, 78, 8A and 8B, are schematic diagrams of a preferred electrical control system; 1

FIG. 9 is a diagrammatic elevationalview of the machineside'control panel;

FIG. 10 is a diagrammatic elevational view ofthe remote control panel; and I FIG. 11 is a diagrammatic view showing the ram sections in various positions.

DETAILED DESCRIPTION OFLTHE PREFERRED FORM OFTHE INVENTION Reference character 10 =designates generally the ram chamber portion of a stationary compactor.Such portionmay correspond in constructionto that disclosed in U.S. Pat. No. 3,289,572, and is preferably provided with. similar safety means for preventing damage in event. of overstressing, although such safety means forms no part of the present invention and for clarity of illustration is not shown. Means (not. shown) are also provided for releasably couplingthccompaction chamber to a container to be fillednhe coupling means it-. self being omitted and the container only diagrammatically indicated at l2,thcse parts also beingdisclosed in the aforementioned US; patents and forming in themselves no pan of the present invention.

A reurwardly extending frame portion 15 rigid with the ramming chamber 10 contains guideways and hydraulic cylinder and. piston assemblies for .actuating the rammingv means. The ramming means comprises complemental lower.

and upper ram sections respectively designatedltS-and 18, both of which are of rectangularcross section and of such. uniform width as to have a smooth slidingfitzwithin the interfront faces of the ram sections are aligned, as shown in FIG. 2,

nal sidewalls of the ramming chamber. The vertical height of the lower ram section l6 is approximately twice that of the.

upper section 18 whichis slidable thereupon. The total height ofthe two sections is substantially less than the effective height of the ramming port 29, the upper limit of which is defined by the rigid header bar 23.'In a preferred machine the overclearance (X," FIG. I) thus defined is approximately 10-..

inches, which provides sufficient clearance for virtually all materials of an extremely rigid nature apt to be encountered, such as railroad ties, cement blocks, and the like,- and the ram assembly is arranged to enter the container a distance substantially exceeding theoverclearance', so that .themachine will tend to clear itself of and reorient suchlarge imcompressible materials in a manner to reduce the danger of overstressing. Thisis brought out-in greater detailinsaid-prior U.S.Pat. No. 3,403,620. In a preferred machine constructedin accordance with the present invention, the height of the upper ram section is 11 inches and the height of the lower ram section 16 is 24% inches. At full extension, the ram assembly projects into the container approximately 18 inches. I

The'lower ram section 16 is powered-by apair of. laterallyjectingbottom iportion 30rextending the fullwidthof and for-f Y I wardly from suchramsection, the projection 30 functioning to compress andlift the lowest portion of the contents of the container. Locating means 3] on topjof the projection 30 are provided for a tubularor pipe-type closure element for the container, and spaced thereabove a pair of additional brackets 32 are provitled on the front of the lower ram section, for a secondsuch-closure element. The method of use of such closure elements is described in the aforementioned U.S. Pat. No. 3,250,414.

The two ram sections, during normalcperation tend to move at the same speed, although duringsuch normal operation they are not mechanically connected to each.other. The, specific means. for supportingand guiding the ram sections and. the cylinderand piston assemblies, and other structural elements, are subject to variation as engineering. considerations may dictate. In the preferred construction shown", the, side plates of the section 15 which enclose the sides thereof act as structural members and carry'the slideway portions as 33, 34. Downwardly directed guiding elements 39 are also provided extending along the sidewalls of the compaction chamber .and preventingthe upper section from moving up,- wardly away from the lower section 16.

InFIG. 2 the ram sections areshown in.their fully retracted or out" position, in which. they define the rear wall of the compaction chamber. The top plate,26 of the lower sectionv 16. is approximately 30 inches long, in the'embodiment described. A forward bottom plate 27 of the upper ram section slides on. the top plate 26 of the lower section and is of the same length.,

A clearance space 35. corresponding. to the combined thickness of the two plates, 26, 27 is thus left in the area to the reariof such plates. An abutment block 36 rigidly secured to the bottom of the upper sectionl8 projects downwardly below the extending plane of the topof plate 26. When the the front end of abutment block 36 is l4 inches from. the rear end of plate 26. Block 36 thus limits to l4 inches to the extent to which the. top section can lead the lowersection. Another abutment block.38 is secured to the topof the lower ramsection farther tothe rear and projects upwardly to interfere with abutment block 36 to limit the extent to which the upper ram can trail the lower ram (to a maximum of 24 inches in the preferred embodiment illustrated).

upper ram is projected (to the extent. of 14 inches, in the embodiment illustrated) with respect to the lower ram,- to maintain the two ram sections in such relative position under certain conditions, as will be explained hereinafter. Latch hook 42 is actuatable upwardly by a lifting arm 45 fast upon the pivot bar 44. An actuating shoe 46 is carried by the stationary frame structure 15 at a position to be engageable by the arm 45 when the lower ram section 16 is projected sufficiently.

The shoe 46 has a horizontal top and sloping ends and in the preferred embodiment illustrated its flat top is approximately 18 inches long. It is so located that if the shoe is in the elevated position, the lifting arm rides on the shoe while the position of the lower ram is; such that its frontface is not more than Zfcct lO-inches behind (to the left of) the header bar 23 and not less than 14 inches to the left OF THE HEADER BAR. If at the same time the front face of the upper ram is in the region to the left of the'header bar but not more than 18 inches to the left, which'is the range within whichjamming of the upper ram could conceivably occur (due to a large incompressible load overlying the front top corner between the upper ram and the header bar) the latch book 42 can be used when the lower ram is 14 inches to the left of the upper ram, and if handle has been raised to move the shoe 46 to raised position, the latch hook will be lifted by the shoe 46 to engage behind-keeper block 40. v I

If forward movement of the upper ram is arrested by an incompressible load (which arrest would occur within the aforementioned l8-inch jamming range) the lower ram continues forwardly until it is arrested, whcrcal'tcr the pressure in the system rises beyond a predetermined value (cg. 800 psi.) and pressure switch 84.trips, to actuate solenoid US, which moves value 116 to the left and dumps the pressure in cylinder '24, provided limit switch 114 is'also closed, completely relaxing the upper ram. Limit switch 114 is held closed by the upper ram when such ram is within a predetermined distance (e.g. l8 inches) of the header bar in either direction. The lower ram then moves forwardly to the limit of its stroke or to the extent permitted by the lost motion between block 36 and block 38, as noted, and this normally results in freeing the jam.

' It will be appreciatcdthat the range within which jamming might occur depends upon the service for which the machine is designed and the material to be handled. The forward movemerit of thelowerram after the upper ram has been relaxed tends to create a pocket or tunnel in any material in the container near the opening. If the machine is designed for service conditionswhich are severe as to possible jamming, the extent of lost motion between the block's 36-38 may be increased, to pennit the lower ram to advance more than 24 inches beyond the upper ram, in order to createa deeper pocket in event the upper ram is jammed at a position relatively far from the header bar. although the greater overclearancev above the lower ram'and the arresting and relaxing of the upper ram as the lower ram continues inwardly normally frees the jam so that normal operation of the compactor can continue. If the unit remains jammed, however, the lower ram is then retracted, while the upper ram remains stationary, until the lowe'rram is-14 inches to the rear of the upper ram (which is As shown in FIG. 2, the shoe 46 is movable to the raised position, in which it is shown in full lines iii that view, in which position it is operative to move the latch piece upwardly to the locked position in the manner described, and is also movable downwardly .to the position in which it is shown in dotted lines, in which it is clear of the path of the, arm 45, allowing the ram sections toremain independent regardless of their position. Movement of the shoe 46 to these two positions is effected manually by a handle 51 which extends from the side of the frame extension 15 and which actuates the shoe through the agency of parallelogram linkage 52. Handle 51 actuates the parallelogram linkage 52 through the agency of an interposed torsion spring 53, so that the shoe can be forced downwardly to the lifting arm in the event the shoe operating handle has been raised at an improper time so that the latch book 42 cannot be raised.

FIGS. 6, 7A, 73, 8A and 8B show in a diagrammatic form the hydraulic and electrical elements of a system for con trolling such a machine for two stations, one (FIG. 9) at the machine and the other (FIG. 10) remotely located, for example, on the upper loading floor. I

In order to achieve a more rapid advance at light rarn loads,

two high capacity pumps 61, 62 driven from a common drive motor are employed. In the embodiment referred to each has an output of 55 gallons perminute.

Pump 61 delivers its output via conduit 64, motor-operated four-way valve 65 and check valve 66 to a main forward line the position'of engagement of plate '26 with block 36 and which position, as indicated above, also permits the latch book 42 to be raisedbehind the keeper block 40). Forward power is then applied to all threecylinders, and the two'lower ram cylinders 21, 22 thus also apply power to the upper ram, urging it forwardly with greater force. Inasmuch as the upper ram was also relaxed, and may have retracted slightly, due to the resiliency of the jammed material, and because room for such material has been created by the pocketing effect resulting from the independent advancement ofthe lower ram, the jammedmaterial willthen normally be forced into the contamer.

refer to ram movements; inward" or l'orward'- being the I direction .in which the rams move into the container and "out ward and rearward being the direction in which the ram moves out of and away from the container. Pressure limiting v valve 77 limits the output pressure of pump 61 to {e.g.) 900 p.s.i., while pressure limiting valve 78 limits the output pressure of pump 62 to (e.g.) 1800 p.s.i.

The electric motor 80 of valve is controlled by a pressure.

switch 84 connected to the output of pump 62. At the start, both valves 65 and are moved to the right from the centered drain position in which they are shown, so that fluid from both pumps is delivered via main line 68 to the rear ends of the cylinders 21, 22 and 24 to move the rams inwardly at full speed. When the resistance encountered by the rams is sufficient to cause the output pressure of pump 62 to rise to a predetermined value, e.g., 800 p.s.i., switch 84 actuates motor to shift valve 65 to the drain position shown in FIG. 6, while the output of pump 62 continues to be delivered via valve 75 at the higher pressure to move the rams forwardly toward the full in position at half speed. Check valve 66 prevents the oil pumped by pump 62 from returning to drain at such time.

When the fourway valves 65 and 75 are moved to the left by their respective motors 80, 82, which occurs when limit switch 126 (FIG. 7B) closes in response to attainment of full in position by the upper ram 18, the connections to and from the main lines 68, 76 are reversed, and fluid from both pumps is delivered to main return line 76 from which it is distributed to the forward ends of the cylinders to retract the rams at full speed. At such time the oil from the rear ends of the cylinders returnsto the sump via conduit 68 and valve 75; and'through dump valves 91, 92, 94. If during such return-movement of the pistons to retract the rams any jamming should occur which via valve 65 is prevented by a check valve 88 in the conduit 86 leading from the valve 65 to the distribution line 76.

In view of the relatively high fluid volume displaced from t the rear ends of the cylinders during outward movement of therams as compared to the fluid volumes of the forward or rod ends of the cylinders, one of the dump valves 91, 92, 94 is connected to the rear end of each cylinder and is automatically opened during outward movement, and closed during inward movement. Each dump valve is actuated by a hydraulic actuator 95, 96, 98. The actuators 95, 96 of the dump valves of the lower ram cylinders are directly connected to the conduit 100 which communicates with a dump valve control pilot valve 102 which is actuatable by a solenoid 104. A limit switch 105 actuated by valve motor 82 energizes solenoid 104 to move valve 102 to the left from the position shown, in which it delivers fluid to all three of the hydraulic servos 95, 96, 98. Switch 105 maintains the solenoid 104 deenergized and valve 102 in such position, so the dump valves 91, 92, 94 are closed, during inward rarn movement. Switch 105 energizes the solenoid 104 to move valve 102 to the left and vent the servos 95 and 96 during outward movement of the rams. This action occurs because servos 95,96 are vented through valve 102, so that valves 91, 92 which are biased to drain move to the right and dump the rear ends of the cylinder 21, 22. It will be noted that normally the servo 98 is similarly vented through valve 102 at this time via the left section of a manual valve 106, which bridges a check valve 108 so that fluid may blow from the servo 98 around the check valve 108 and to the line 100 and via valve 102 to drain. Under such conditions the rear ends of all of the ram cylinders are fully vented.

Under certain conditions it may be desired to permit the lower ram section to move rearwardly without moving the upper secton until the full independent movement (eg. 14 inches) has been reached, either to correct a jam as explained above or to prevent more material from dropping in front of the rams. This may be accomplished by means of the manual valve 106, which, when moved to the left against its bias blocks the connection to the servo 98 from the line 100, while outflow from servo 98 is then also prevented by a check valve 110 in line 111 leading from distribution line 76 to valve 106. 'After the fullindependent movement is completed,.the lower ram pulls the upper ram rearwardly, and fluid escapes from the rear end ofupper ram cylinder 24;via valve 120, lines 6968 and valve 75. This permits thelowcr ram to be moved back to a position which allows the closure members to be placed on the supports 31, 32 by inserting them through the ports 37, as taught in US. Pat. No. 3,250,4 l 4, while the upper ram section 18 projects forwardly far enough to prevent any material which may during the pinning operation be dumped into the chute or hopper from entering the container or interfering with the pinning operation. Such independent rearward movement of the lower ram also enables the two ram sections to be latched together by means of the hook 42, if the shoe 46 is raised, as noted above. It will be appreciated that in event of a plugging or resistant load at the top which tends to restrict forward movement of the upper ram section, the lower ram section tends to advance and to be forward of the upper section to the extent of the greater independent travel permitted in such direction (eg 24 inches), so that under such conditions of plugging or high resistance in the upper area, such holding back of the upper ram section leaves aneffective ram clearance equal to the distance between the top of the lower ram and the header bar (dimension X" plus the height of the upper ram section, 2 l '76 inches).

1f the pressure developed due to the obstruction is over 800 pounds, pressure switch 84 will be tripped. A limit switch 114, in series with a circuit which also includes contacts I 13 operated by pressure switch 84 r and solenoid 115, is held closed by the lower ram whenever the lower ram is in a position relatively close to alignment with the header bar 23. In the embodiment of the invention referred to, limit switch 114 is held closed when the ram is within 18 inches on either side of a vertical line to the header bar. Energization of solenoid 115 moves valve 116 to the left, delivering fluid from pump 62 to hydraulic servo unit 118 which closes shutoff valve 120 incorporated in the line 69 which connects the main forward line 68 to the rear end of the upper ram cylinder 24. The upper ram is therefore stopped while the lower ram continues to move forwardly. At the same time a drain line 122 which shunts the valve 120 vents the rear end of cylinder 24 through valve 116. In flowing to drain through valve 116 the fluid from the rear end of cylinder 24 passes through a check valve 124 and restriction 125, relaxing the pressureon the upper ram, which may then move back a short distance to release any pinching action between the upper ram and the headerbar and permit the lower ram to continue to move inwardly pulling the material under the enlarged opening beneath the header bar. When the lower ram has moved inwardly to the indicated inner limit of the range of closure of limit switch 114 (18 inches) beyond the header 'bar) the lower ram hasa.

remaining travel of approximately 8 inches, during whichlimit switch 114 is opened, deener'gizing solenoid 115, reopening the valve 120 and permitting fluid pressure to force the upper 75 to cause retraction of the ram sections. If the machine i's'so completely blocked that the upper ram cannot move forwardly to trip the limit switch 126, which may be caused either by such a complete blockage or a tripout of one ofthe safety switches previously referred to (shown at SLS, 6LS, 7LS of,

the line diagram FIG. 7) it may 'of course be necessary to i manually unplug machine.

lt will be recognized that the contents of the container may be of a nature which possesses considerable resiliencyflwhen the load is under compression and the compressive force is suddenly released, the tendency of the load to reexpand may drive the ram sections and connected pistons outwardly very quickly, tending to create a negative pressure in the cylinders at the forward or rod ends which could be harmful to the sealing means for the piston rods. Under such conditions any negative pressure at the rod ends of the cylinders is relieved through check valve 130 which ,vcnts such areas under vacuum, but closes under positive pressure.

Control of reversal of the motor operated valves and to rcproject the rams from full out position is effected by limit switch 133 actuated by the lower ram section. In the preferred embodiment illustrated, the total ram travel, which is the same for both ram sections, is approximately 12 feet. The top plate 19 of the upper ram section 18 is strong enough to withstand the impact of heavy objects and dimensioned so that when fully projected it effectively blocks the full cross section of the ram chamber.

This Detailed Description of Preferred Form of the'invention, and the accompanying drawings, have been furnished in compliance with the statutory requirement to set forth the best mode contemplated by the inventor of carrying out of the invention. The prior portions consisting of the Abstractof the Disclosure and the Background of the Invention are furnished without prejudice in an effort to comply with administrative requirements of the Patent Office.

What is claimed is:

What is claimed is:

1. Apparatus for containerizing and compacting waste material or the like, of the type which includes a generally rectangular ram chamber having a top charging opening, a

ramming port in one side, a rigid header bar bounding the top of the port, and rectangular ramming means spaced below the header bar and movable across the bottom of the chamber and outwardly beyond the bar through the port to extend into a container, characterized in that the ramming means comprises two superposed relatively slidable sections.

2. Apparatus as defined in claim 1 wherein said sections have limited lost motion travel with respect to one another.

3. Apparatus as defined in claim 2 including separate hydraulic cylinder and piston-type actuating means for each of said sections, and a common hydraulic supply system for the actuating means of both sections, whereby fluid delivery to the 4. In combination with means of claim 3, relaxing means for said upper secton responsive to a predetermined relatively high pressure in said system for-disabling and relieving the fluid pressure in the actuating means of the upper section without disabling the actuating means of the lower section.

5. Apparatus as defined in claim 2 including releasable means for locking said sections together to prevent such lost motion.

6. Apparatus as defined in claim 2 include separate hydraulic cylinder and piston-type actuating means for each of said section, a common hydraulic supply system for the actuating means of both sections, whereby fluid delivery to the separate actuating means, and the rate of movement of the sections, is

variable in response to differences in the resistance encountered by said sections, and releasable means for locking said sections together to prevent such lost motion.

7. Apparatus as defined in claim 2 include separate hydraulic cylinder and piston-type actuating means for each of said sections, a common hydraulic supply system for the actuating means of both sections, whereby fluid delivery to the separate actuating means, and the rate of movement of sections, is variable in response to differences in the resistance encountered by said sections, and releasable means for locking said sec tions together with the upper section projecting forwardly farther than the lower section to prevent such lost motion and operatively connect all of the actuating means to both sections. I

8. Apparatus as defined in claim 1 including separate hydraulic cylinder and piston-type actuating means for each of said sections, and a common hydraulic supply system for the actuating means of both sections, whereby fluid delivery to the separate actuating means, and the rate of movement of the sections, is variable in response to differences in the resistance encountered by said sections. W

9. In combination with apparatus as defined in claim 8, means for controlling delivery of fluid to at least one of the actuating means for said sections independently, to permit mov ing the sections to different positions relatively to each other.

10. in combination with means as defined in claim 8, in-

dividual control means of the actuating means of each section,

whereby independent projecting and retracting movement can be imparted to each section.

11. In combination with means as defined in claim 8, relaxing means for said upper section responsive to a predetermined relatively high pressure in said system for disabling and relieving the fluid pressure in the actuating means of the upper section without disabling the actuating means of the lower section.

12. in combination with means as defined in claim 11, means responsive to the position of the upper section for disabling said relaxing means when the forward end of said section is beyond a predetermined distance from said header bar.

l3v Apparatus as defined in claim I wherein said sections are of rectangular cross section, the vertical dimension of thc lower section being substantially greater than that otthe upper section.

[4. Apparatus as defined in claim I wherein'thc sections occupy the full width of the chamber and the upper section has a flat impervious top ofa length which is not less than the sum of the length of the chamber and maximum distance which said section extends beyond said chamber and into a container when fully extended.

15. Apparatus as defined in claim 1 wherein the vertical dimension of the upper section is a substantial fraction of the total height of the two sections. 

1. Apparatus for containerizing and compacting waste material or the like, of the type which includes a generally rectangular ram chamber having a top charging opening, a ramming port in one side, a rigid header bar bounding the top of the port, and rectangular ramming means spaced below the header bar and movable across the bottom of the chamber and outwardly beyond the bar through the port to extend into a container, characterized in that the ramming means comprises two superposed relatively slidable sections.
 2. Apparatus as defined in claim 1 wherein said sections have limited lost motion travel with respect to one another.
 3. Apparatus as defined in claim 2 including separate hydraulic cylinder and piston-type actuating means for each of said sections, and a common hydraulic supply system for the actuating means of both sections, whereby fluid delivery to the separate actuating means, and the rate of movement of the sections, is variable in response to differences in the resistance encountered by said sections.
 4. In combination with means of claim 3, relaxing means for said upper secton responsive to a predetermined relatively high pressure in said system for disabling and relieving the fluid pressure in the actuating means of the upper section without disabling the actuating means of the lower section.
 5. Apparatus as defined in claim 2 including releasable means for locking said sections together to prevent such lost motion.
 6. Apparatus as defined in claim 2 include separate hydraulic cylinder and piston-type actuating means for each of said section, a common hydraulic supply system for the actuating means of both sections, whereby fluid delivery to the separate actuating means, and the rate of movement of the sections, is variable in response to differences in the resistance encountered by said sections, and releasable means for locking said sections together to prevent such lost motion.
 7. Apparatus as defined in claim 2 include separate hydraulic cylinder and piston-type actuating means for each of said sections, a common hydraulic supply system for the actuating means of both secTions, whereby fluid delivery to the separate actuating means, and the rate of movement of sections, is variable in response to differences in the resistance encountered by said sections, and releasable means for locking said sections together with the upper section projecting forwardly farther than the lower section to prevent such lost motion and operatively connect all of the actuating means to both sections.
 8. Apparatus as defined in claim 1 including separate hydraulic cylinder and piston-type actuating means for each of said sections, and a common hydraulic supply system for the actuating means of both sections, whereby fluid delivery to the separate actuating means, and the rate of movement of the sections, is variable in response to differences in the resistance encountered by said sections.
 9. In combination with apparatus as defined in claim 8, means for controlling delivery of fluid to at least one of the actuating means for said sections independently, to permit moving the sections to different positions relatively to each other.
 10. In combination with means as defined in claim 8, individual control means of the actuating means of each section, whereby independent projecting and retracting movement can be imparted to each section.
 11. In combination with means as defined in claim 8, relaxing means for said upper section responsive to a predetermined relatively high pressure in said system for disabling and relieving the fluid pressure in the actuating means of the upper section without disabling the actuating means of the lower section.
 12. In combination with means as defined in claim 11, means responsive to the position of the upper section for disabling said relaxing means when the forward end of said section is beyond a predetermined distance from said header bar.
 13. Apparatus as defined in claim 1 wherein said sections are of rectangular cross section, the vertical dimension of the lower section being substantially greater than that of the upper section.
 14. Apparatus as defined in claim 1 wherein the sections occupy the full width of the chamber and the upper section has a flat impervious top of a length which is not less than the sum of the length of the chamber and maximum distance which said section extends beyond said chamber and into a container when fully extended.
 15. Apparatus as defined in claim 1 wherein the vertical dimension of the upper section is a substantial fraction of the total height of the two sections. 